1. Field of the Invention
The invention relates generally to structural connections and more particularly to systems and methods for enhancing structural connection performance and facilitating failure detection.
2. Background
Detection of failures and/or potential failures in fatigue-critical connections in structures has long been problematic. For many years, structural fuses, as depicted in FIG. 1, have been used to assist in detection of fatigue failures. However, due to difficulty with inspection and subsequently early identification of failures and/or potential failures, such structural fuses have not been utilized in many structures.
Connection enhancement methods and systems have existed since the beginning of modern construction. These systems range from cover-plated systems, as depicted in FIGS. 2a & b, to weld tapering and other mechanisms. In the typical reinforcement depicted in FIGS. 2a-b, a primary member 202 is bonded with a reinforcing member 204 via a perimeter fillet weld. In alternate materials and in alternate configurations, various bonding and reinforcing techniques are employed. However, all these techniques involve covering the critical connection with materials that generally do not allow for direct inspection of the underlying connection, and/or prevent ideal stress distribution profiles from being attained.
Additionally, it is important to have an effective method for preventing the propagation of existing fatigue cracks in bridge girders and other structures. A common technique used to prevent such propagation is the drilling of crack-stop holes at crack tips. By doing so, stress concentrations at the crack tips are reduced and fatigue life of the bridge is extended. However, mathematical formulae for determining idyllic sizes of crack-stop holes often results in crack-stop diameters larger than can be practically drilled; physical limitations force crack-stop holes to be undersized in the field. Thus, a method is needed to strengthen and/or expand undersized crack-stop holes.
What is needed is a system and method that can provide fatigue enhancement and, in some embodiments, provide a visual indication of the fatigue state of the connection. It is also desirable to have a method for fatigue enhancement of existing fractures and/or undersized crack-stop holes.